What is your application and criteria for your weld?
Other than additional electrode maintenance (aluminum requires frequent tip dressing), no special concerns that you would not apply to any other materials being RSW.
We qualified some structural aluminum welds for a project a few years back. About the only "problem" we encountered was the inherent void within the weld nugget which we reduced from about 50% of the weld area down to about 20%. I know that sounds like a bit much, but it was what the MIl standard allowed for that weld categorie.
This client originally used GMAW to attach aluminum angles to relatively thin sheet. RSW reduced fabrication costs substantially.